A DETAILED 31,000 YEAR RECORD OF CLIMATE AND VEGETATION CHANGE, FROM
THE ISOTOPE GEOCHEMISTRY OF TWO NEW ZEALAND SPELEOTHEMS

J. Hellstrom, M.T. McCulloch and J.O. Stone

Quaternary Research 50, 167-178. (1998)

Abstract

Uranium-series dating and stable isotope analyses of two speleothems
from northwest Nelson, New Zealand, record changes in regional climate
and local forest extent over the past 31,000 years. Oxygen isotope variation
in these speleothems primarily represents changes in the meteoric waters
falling above the caves, possibly responding to latitudinal changes in
the position of the Subtropical Front in the Tasman Sea. Seven positive
excursions can be identified in the oxygen isotope record, which coincide
with periods of glacier advance, known to be sensitive to northward movement
of the Subtropical Front. Four glacier advances occurred during oxygen
isotope stage 2, with the most extreme glacial conditions centred on 19,000
cal yr B.P. An excursion in the oxygen isotope record from 13,800 to 11,700
cal yr B.P. provides support for a previously identified New Zealand glacier
advance at the time of the Younger Dryas Stade, but suggests it began slightly
before the Younger Dryas as recorded in Greenland ice cores. Carbon isotope
variations in the speleothems record changes in forest productivity, closely
matching existing palaeovegetation records.